profiles of endophyte-infected host plants, particularly for important compounds
such as cannabinoids. As a whole, such systems might serve as models for plant
growth and development studies involvingCannabisendophytes, which could
enhance plantfitness and lead to better cultivation methods of plants with immense
medicinal properties.
20.5 Investigation ofCannabisEndophytes
Employing Antivirulence Strategy
for Attenuation of Virulence FactorsIn addition to discovering endophytes harbored inCannabisplants with the capacity
to produce antimicrobial compounds, the potential of these microorganisms in
effectively disarming the virulence factors of invading pathogens (so called“an-
tivirulence”efficacies of the endophytes) have been studied. For example, the
endophytic fungal isolatesA. nigerandA.flavusextracts were tested for antifungal
activity against plant pathogensColletotrichum gloeosporioidesandCurvularia
lunata, respectively. Different concentrations of endophytic extracts were tested
either alone or in combination with plant extracts (Gautam et al. 2013 ). Interestingly,
the extracts were found highly effective against the pathogens when treated alone or
in combination with leaf extracts as compared to those combined with stem extracts.
This work showed promising antimicrobial efficacies of fungal endophytes, thereby
inhibiting growth of fungal pathogens. Similarly, extracts prepared from endophytic
bacterial isolates ofCannabisplants were tested against generalist harmful bacterial
pathogens likeEscherichia coliandStaphylococcus aureusand the fungal pathogen
Candida albicans(Qadri et al. 2013 ). All these pathogens are reported to be highly
infectious and responsible for colonization and biofilm formations (Claessen et al.
2014 ; Kusari et al. 2015 ). The extracts were compared with broad spectrum
antibiotics effective against bacterial pathogens, namely ciprofloxacin and nystatin.
The extracts of selected endophytic bacterial isolates showed pronounced activity
againstS. aureuswith IC values of 50lg/ml, while others were effective againstC.
albicanswith IC values of 50, 15 and 50lg/ml respectively. Antimicrobial activity
is a strategy where an antimicrobial or antibiotic agent is used to kill microorganisms
or inhibit their growth (Leekha et al. 2011 ). It is compelling that the co-evolution of
endophytes enable them to recognize invading or potential harmful pathogens and
develop strategies like antimicrobial efficacy to counteract them. Thus, exploiting
these endophytic isolates for production of bioactive molecules effective against
biofilm-forming pathogens would serve as an alternative or addition to most widely
used antibiotics. Although such an antimicrobial strategy aids in inhibiting patho-
genic growth, it is also one of the main reasons of inducing drug resistance in
bacteria due to the selection pressure on their growth and survival (Clatworthy et al.
2007 ; Kunzmann et al. 2014 ). Therefore, exploring alternative strategies have
become a major focus of most recent research.
428 P. Kusari et al.